An internal combustion engine is described in German Patent Application No. DE 30 02 701 A1, which describes an internal combustion engine having an exhaust-driven turbocharger that has a shiftable turbine guide mechanism. A computer unit is associated with the internal combustion engine in order to control the delivery of boost air as a function of engine operation. Shifting of the turbine guide mechanism is regulated by way of the computer unit, by the fact that it defines set points. At the same time, an instantaneous actuating movement of actuating elements on the turbine guide apparatus is conveyed to the computer unit. To monitor the functioning of the exhaust-driven turbocharger, monitoring sensors are provided to ascertain the turbine rotation speed, lubricating oil temperature, and wear phenomena or imbalances. If the signal of a monitoring sensor deviates impermissibly from a set point, the computer unit prepares a malfunction indication datum.
German Patent Application No. DE 39 42 499 A1 describes controlling the air throughput of a common intake air line, downstream from two parallel exhaust-driven turbochargers, of an internal combustion engine by way of electrical valves, in order to adapt the turbocharger output optimally to the engine's operating state.
German Patent No. DE 195 31 871 C1 describes an internal combustion engine having an exhaust-driven turbocharger whose turbine has a turbine guide mechanism with which the incident flow direction of the exhaust gases onto the turbine blades, and the incident flow cross section itself, can be varied. The turbine guide mechanism is adjustable via an actuating motor for whose function a control unit is provided. The control unit with actuating motor makes it possible, by displacing the turbine guide mechanism, to regulate the instantaneous boost pressure sensed by way of a pressure sensor. This makes it possible to establish boost pressure set points which correspond to a favorable boost pressure characteristics diagram that depends on the engine speed and injected fuel volume.
German Patent Application No. DE 195 47 994 A1 describes an internal combustion engine having two exhaust-driven turbochargers, working in parallel, which deliver fresh air into a common intake system or alternatively into two separate intake systems for two cylinder banks of the internal combustion engine. A similar arrangement having two parallel turbochargers for separate intake sections is disclosed in German Patent Application No. DE 38 32 965 A1; in this, by way of a pressure sensor and a differential pressure sensor or by way of a single pressure sensor that can selectably be switched to one of the two intake sections at a time, the pressures in the intake sections are sensed and can thus be regulated to identical pressure values.
With the conventional arrangements having two parallel turbochargers delivering into one common intake line, it is possible with a conventional boost pressure control system only to ensure that the desired boost pressure is reached; it is not possible, however, to ascertain the weighting with which the two turbochargers contribute to creation of the boost pressure. In normal operation, with an engine configuration that is symmetrical in terms of air delivery and with identical exhaust gas angles of incidence for the two turbochargers, it can be assumed that the contributions of the two turbochargers are identical. If, however, an electrical or mechanical fault occurs in the delivery capacity adjusting unit of one or both turbochargers, this can result, even though the overall delivered volume is correct, in highly inhomogeneous delivery capacities for the two turbochargers; this cannot be detected by the boost pressure control system and results in a malfunction that can cause mechanical damage to one or both turbochargers.